A low complexity two-stage precoding and user grouping scheme for full-dimension MIMO systems

Multiuser precoding is studied for full-dimension MIMO (FD-MIMO) systems, where a new dual precoding scheme is proposed to reduce the complexity of computing the precoding matrix´s. In the proposed algorithm, the precoding matrix design is decomposed as outer-beamforming matrix (OBM) design and inner-beamforming vector desgn follow the dual precoding idea. And a vertical beamforming based OBM design is proposed which transforms the complex OBM design into vertical beam-former design for each column of antennas, through which the complexity can be apparently reduced. Besides, an iterative SLNR based algorithm is developed to obtain the vertical beamformers. A simple vertical channel correlation based user grouping scheme is also proposed to enhance the virtue of the proposed scheme. Simulation results show that the proposed scheme can well exploit the advances of FD-MIMO and improve the spectrum efficiency with reduced complexity.